(a) Technical Field
The present invention relates to a method for producing a brake disc, particularly a method for producing a brake disc by casting gray cast iron and ductile cast iron, an apparatus for producing a brake disc, and a brake disc produced thereby. The present method saves costs and provides a lightweight brake disc.
(b) Background Art
Worldwide automobile companies concentrate significant efforts on technological developments for improving fuel efficiency due to limited petroleum energy resources and its impact on the environment and climatic change. Among the technological developments aimed towards improving fuel efficiency, decreasing vehicle weight without performance deterioration attracts public attention.
In particular, a weight reduction in a lower part of the vehicle directly influences the performance and fuel efficiency of the vehicle. Since a decrease of an unsprung mass (i.e. the mass of the suspension, wheels, and other components directly connected to them, rather than supported by the suspension) associated directly with a wheel driving load greatly improves fuel efficiency, associated technologies have been very rapidly advanced in recent years.
Among these technologies, much attention has been focused towards the development of a method that reduces the weight of a brake disc, which occupies a primary weight of the unsprung mass, without deteriorating performance.
In a brake disc 10 in the related art, as shown in FIG. 1, both a hat part 30 to be mounted on a hub and a disc plate 20 where friction is made while braking are manufactured by an organization of flake graphite which forms gray cast iron. This provides excellent braking characteristics such as a vibration reducing capacity, a damping capacity, a heat dissipating capacity, and a lubricating function.
However, such a brake disc is heavy due to the specific gravity of gray cast iron, which is equivalent to 7.2 g/cm3. This heavy weight is a primary factor that causes a deterioration in the fuel efficiency.
Therefore, a brake disc using a heterogeneous material needs to be developed in order to reduce the weight of the brake disc. Further, the disc structure must satisfy performance requirements, such as the heat dissipating capacity or deformation resistance, while providing durability by perfectly coupling two heterogeneous materials.
The existing technology configures the brake by coupling a hub, made of heat treatment forging steel, to a disc, made of a single material such as gray cast iron. However, the parts much be coupled, which results in an unnecessary weight increase, can further result in an inadequate coupling force between the parts, and provides for more a more complex assembly process.
Matters described as the background art are just to improve the background of the present invention, but it should not be understood that the matters correspond to the related art which has been already known to those skilled in the art.